Coolant loss, bike ran bad during torturous mud race

[zio]

update.... any more insight on my overheating?

Did a search, hard to find right info on this specific topic.

I did a harescramble yesterday. It was really, really muddy, and I did a lot of abusing the motor to get up slimy hills. Towards the end of the 2nd lap (I did 3 laps in 90 minutes), the bike started running funny. I noticed the sound, first. It got really deep, sort of boggy sounding. Then I noticed it surging a little, like it was pinging, when at low rpms, or when coasting. Finally, I noticed the sound got deeper, and the power was definitely decreasing.

At the end of the race, riding through the pits back to my truck, it was really surging & doing that 2-stroke ping thing (rrrrrrrmmmm DDDDRRRRrrrrrrrrrrrrrrrmmmmmmDDDDRRRRR.....).

I did check the airfilter, and it was clean (muddy race, no dust). But the bike had at least 50 lbs of mud caked on it. Maybe more. I had at least 25 lbs on me & my gear.

I washed it today, started it up, & it ran fine. Then I thought to check the radiator- bone dry. Well, I couldn't see any in there at least. Do you think I have anything to worry about?

 

[Studboy]

I would definately pull the cylinder off and check the bore and the piston.

My buddy had the coolant bolt rattle out on his 250 at the sand dunes and we didn't notice it. We ran it all day like that, we were even drag racing it. It would do fine for about thirty seconds of WFO throttle, and then it would bog out (piston expanding into the cylinder!). We kept messing with jets and fuel but could never cure it.... finally after about 4 hours of abuse the piston burned down.

Unfortunately the plating also bubbled up and was worn through on the exhaust side. I couldn't believe that it ran that long without any coolant!

 

[Detonator]

Zio,

Have you changed your oil yet? Just checking to see if it came out milky, which would indicate a water pump seal issue.

For what it's worth, my buddy's 525 EXC used to boil over in low speed/high load situations like mud or tight bushwacking. He got an overflow bottle system, which essentially captures ejected fluid when too hot, and then sucks it back in when the engine cools. There are times when the bottle is filled to capacity under high load, but will empty as soon as he gets into second gear speeds. There is no net loss of fluid at the end of the day, but there certainly would be if he didn't have the catch bottle. Hope you didn't cause any damage to your Pumpkin.

 

[nickyd]

drain the coolant first and see what comes out.

 

[Wolf]

Zio, I would drain the coolant - whats left of it first, and then determine whats up.

 

[jumpingjoe628]

I went to a harescramble at Budds Creek a couple of years ago and went throught the same conditions on the track. It was like 95 degrees and 100% humidity after a big rain storm. Right before the first lap was over I got a flat front tire, then about a mile or so in on the second lap the plastic tee for the radiator hoses exploded and I had hot coolant everywhere. By the time I made it close enough to get back to the pits I also had no front brakes due to the mud. The bike was surging like you described all the way back to my truck. Anyway, it turned out I had more damage than just the plastic tee..... After a piston, a few new head gaskets, resurfacing the head, and buying an aftermarket head I discovered that the cylinder had cracked near the base and went up and over one of the base studs to the other side and back down to the base line. I just got it welded and the base was re-turned on a lathe and I got a thicker base gasket to compensate. I also got the cylinder re-plated just as insurance and it runs great now. This problem had plagued me for a year and a half. Take it apart and check everything !!!!

 

[zio]

Okay, first will be drain radiators to see what's left. Next will be change the oil. Then, I'll give it a good cleaning & pull the head & take a look.

 

[zio]

Changed the oil, and aside from being really dirty looking, and a little burnt smelling, there was no signs of coolant. The radiators took almost a whole liter of water. Pulled the pipe, and the piston looks pristine. ;)

Took it for a spin, & it ran fine. Do I bother now with pulling the head off?

 

[zio]

anyone?

 

[Studboy]

If it was my bike, I would pull the head off, just to make sure that it isn't going to grenade and leave me stranded somewhere.

 

[gwcrim]

Try a compression check.

You've heard it before.... if it ain't broke, don't fix it.